A Comparative Evaluation of the Measurement Properties of Three Histological Indices of Mucosal Healing in Ulcerative Colitis: Geboes Score, Robarts Histopathology Index and Nancy Index

Abstract

Background and Aims: To inform their future use in regulated clinical trials to evaluate treatment efficacy hypotheses, the measurement properties of three histological indices, Geboes Score [GS], Robarts Histopathology Index [RHI] and Nancy Index [NI], were evaluated among patients with ulcerative colitis. Methods: Analyses were conducted on data from a Phase 3 clinical trial of adalimumab [M14-033, n=491] and focused on evaluating the measurement properties of the GS, RHI and NI. Specifically, internal consistency and inter-rater reliability, convergent, discriminant and known-group validity, and sensitivity to change were assessed at Baseline, and at Weeks 8 and 52. Results: Internal consistency for the RHI showed lower alpha [α] values at Baseline [α=0.62] relative to Weeks 8 [α=0.82] and 52 [α=0.81]. The inter-rater reliability values of RHI [0.91], NI [0.64] and GS [0.53] were excellent, good and fair, respectively. Regarding validity, Week 52 correlations were moderate to strong between full and partial Mayo scores and Mayo subscale scores and the RHI and GS, and were weak to moderate for the NI. Significant differences between mean scores of all three histological indices were observed across known-groups based on Mayo endoscopy subscores and full Mayo scores at Weeks 8 and 52 [p<0.001]. Conclusions: The GS, RHI and NI are each capable of producing reliable and valid scores that are sensitive to changes in disease activity over time, in patients with moderately to severely active ulcerative colitis. While all three indices demonstrated relatively acceptable measurement properties, the GS and RHI performed better than the NI.